306
FXUS21 KWNC 281930
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 28 2025
SYNOPSIS: MID-LEVEL LOW PRESSURE FORECAST DURING WEEK-2 FAVORS COLDER THAN
NORMAL TEMPERATURES OVER MUCH OF THE NORTHWESTERN CONTIGUOUS U.S. (CONUS), AND
EXTENDING INTO THE NORTHERN ROCKIES AND PLAINS. ADDITIONALLY, ENHANCED ONSHORE
FLOW IS LIKELY TO RESULT IN ROUNDS OF HEAVY PRECIPITATION ACROSS THE WEST
COAST. HEAVY SNOW IS MOST LIKELY ACROSS THE HIGHER ELEVATIONS OF THE CASCADES,
KLAMATH, AND SIERRA NEVADA MOUNTAINS. HOWEVER, SNOW OR WINTRY WEATHER CANNOT BE
RULED OUT OVER LOWER ELEVATION AREAS INCLUDING THE CITIES OF PORTLAND, OR AND
SEATTLE, WA DUE TO THE ANOMALOUSLY COLD AIR MASS PREDICTED TO BE IN PLACE.
TOWARD THE MIDDLE OF THE PERIOD, A SURFACE LOW IS PREDICTED TO EJECT EASTWARD
BRINGING INCREASED CHANCES OF HEAVY SNOW ACROSS THE NORTHERN TIER, WITH AN
ENHANCED RISK OF HEAVY RAIN OVER THE EASTERN HALF OF THE CONUS. MID-LEVEL HIGH
PRESSURE FAVORS INCREASING CHANCES FOR NEAR TO ABOVE NORMAL TEMPERATURES ACROSS
THE SOUTHERN AND EASTERN CONUS DURING THE PERIOD.
HAZARDS
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE PACIFIC
NORTHWEST, WED-THU, FEB 5-6.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE
NORTHWESTERN CONUS AND EXTENDING INTO THE NORTHERN ROCKIES AND PLAINS, WED-SAT,
FEB 5-8.
SLIGHT RISK OF HEAVY SNOW ACROSS PORTIONS OF THE CASCADES, KLAMATH, AND SIERRA
NEVADA MOUNTAINS, AND ALSO INCLUDING LOWER ELEVATIONS OF WASHINGTON AND OREGON,
WED-SAT, FEB 5-8.
SLIGHT RISK OF HEAVY SNOW ACROSS PORTIONS OF THE NORTHERN AND CENTRAL ROCKIES,
NORTHERN PLAINS, UPPER MISSISSIPPI VALLEY, AND NORTHERN GREAT LAKES, WED-SAT,
FEB 5-8.
SLIGHT RISK OF HEAVY SNOW ACROSS PORTIONS OF NEW ENGLAND, FRI-SUN, FEB 7-9.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE PACIFIC NORTHWEST AND
NORTHERN AND CENTRAL CALIFORNIA, WED-THU, FEB 5-6.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS MUCH OF THE EASTERN CONUS, WED-SUN,
FEB 5-9.
SLIGHT RISK OF HIGH WINDS ACROSS MUCH OF THE WESTERN CONUS, WED-SAT, FEB 5-8.
DETAILED SUMMARY
FOR FRIDAY JANUARY 31 - TUESDAY FEBRUARY 04:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY FEBRUARY 05 - TUESDAY FEBRUARY 11: TROUGHING IS FORECAST ACROSS
THE NORTHWESTERN CONUS DURING WEEK-2 RESULTING IN BELOW-NORMAL TEMPERATURES
ALONG THE WEST COAST AND INTO PARTS OF THE NORTHERN ROCKIES AND NORTHERN
PLAINS. THE MOST ANOMALOUS COLD IS PREDICTED TO BE ACROSS THE PACIFIC
NORTHWEST, WITH THE GEFS GENERALLY ON THE COLDER SIDE OF THE GUIDANCE. THE GEFS
AND ECENS PROBABILISTIC EXTREMES TOOLS (PETS) ARE NOT AS ROBUST COMPARED TO
YESTERDAY, BUT STILL DEPICT AT LEAST A 40 PERCENT CHANCE THAT MINIMUM
TEMPERATURES FALL BELOW THE 15TH CLIMATOLOGICAL PERCENTILE EARLY IN THE PERIOD.
THE UNCALIBRATED 0Z ECENS AND GEFS BOTH DEPICT SUBFREEZING TEMPERATURES OVER
COASTAL AREAS, WITH TEMPERATURES IN THE LOWER 20S DEG F IN THE GEFS. A MODERATE
RISK OF MUCH BELOW NORMAL TEMPERATURES IS HIGHLIGHTED ACROSS COASTAL WASHINGTON
AND OREGON, FEB 5-6, CORRESPONDING WITH THE LARGEST PREDICTED NEGATIVE
TEMPERATURE ANOMALIES AND WHERE COLD WEATHER HAZARDS CRITERIA IS MOST LIKELY TO
BE MET. THE 0Z ECENS IS QUICKER TO WEAKEN THE TROUGH OVER THE NORTHWEST
COMPARED TO THE GEFS, AND THEREFORE THE ECENS DEPICTS A QUICKER WARMING TREND
WITH A DIMINISHING SIGNAL FOR HAZARDOUS TEMPERATURES IN THE CORRESPONDING PET
BY THE MIDDLE OF THE PERIOD. DUE TO THE INCREASING UNCERTAINTY, THE SLIGHT RISK
FOR MUCH BELOW NORMAL TEMPERATURES IS ONLY VALID THROUGH FEB 8. THE SLIGHT RISK
AREA EXTENDS ACROSS THE NORTHERN ROCKIES AND PLAINS WHERE SUBZERO TEMPERATURES
ARE POSSIBLE. WHILE THESE TEMPERATURES ARE CONSIDERABLY COLDER COMPARED TO THE
COASTAL PACIFIC NORTHWEST, IT IS LESS CERTAIN IF TEMPERATURES WILL REACH THE
VERY COLD CRITERIA ACROSS THESE AREAS, JUSTIFYING ONLY A SLIGHT RISK.
ALONG WITH THE COLD TEMPERATURES, AN ENHANCED ONSHORE FLOW PATTERN ASSOCIATED
WITH THE TROUGHING FAVORS PERIODS OF HEAVY PRECIPITATION ACROSS THE WEST COAST.
THE INTEGRATED VAPOR TRANSPORT (IVT) TOOL DERIVED FROM THE ECENS AND GEFS
DEPICT AT LEAST A 50 PERCENT CHANCE IVT VALUES EXCEED 250 KG/M/S ALONG THE
OREGON AND CALIFORNIA COAST LATE IN WEEK-1, WITH DECREASING PROBABILITIES
CONTINUING INTO THE OUTSET OF WEEK-2. THE UNCALIBRATED 0Z ECENS AND GEFS DEPICT
A REGION OF HEAVY PRECIPITATION OVER THESE AREAS ON DAY-7, BUT LINGERING
MOISTURE CONTINUES TO SUPPORT A SLIGHT RISK OF HEAVY PRECIPITATION, FEB 5-6.
BEYOND THIS PERIOD, INTERMITTENT CHANCES OF ENHANCED PRECIPITATION ARE LIKELY
TO CONTINUE ACROSS THE WEST COAST, ALTHOUGH RIDGING DEPICTED ALONG THE WEST
COAST IN THE ECENS AND CMCE MAY FAVOR A DRYING TREND LATER IN WEEK-2. THE COLD
AIR MASS IN PLACE ACROSS THE PACIFIC NORTHWEST DURING THE FIRST HALF OF THE
PERIOD SUPPORTS ENHANCED CHANCES OF HEAVY SNOW OR WINTRY WEATHER EVEN IN LOW
ELEVATION AREAS INCLUDING THE CITIES OF PORTLAND, OR AND SEATTLE, WA.
THEREFORE, A SLIGHT RISK OF HEAVY SNOW IS POSTED ACROSS THESE AREAS, AND FOR
THE HIGHER ELEVATIONS OF THE CASCADES, KLAMATH, AND SIERRA NEVADA MOUNTAINS,
FEB 5-8. WITH THE ANOMALOUS TROUGHING ALOFT, AN ACCOMPANYING BROAD SLIGHT RISK
OF HIGH WINDS IS ALSO POSTED ACROSS MUCH OF THE WEST THROUGH FEB 8, WITH AN
INCREASING PRESSURE GRADIENT DEPICTED IN THE GEFS AND ECENS ACROSS THE ROCKIES
AND NORTHERN HIGH PLAINS.
SURFACE LOW PRESSURE IS PREDICTED TO EJECT OUT OF THE TROUGHING OVER THE WEST
BY THE MIDDLE OF WEEK-2, AIDED BY SOME ENHANCED BAROCLINICITY TIED TO
INCREASING MID-LEVEL HIGH PRESSURE OVER THE SOUTHEAST. WHILE THE EXACT TRACK
AND RELATED IMPACTS ARE UNCERTAIN, A SWATH OF HEAVY SNOW CANNOT BE RULED OUT
ACROSS PORTIONS OF THE NORTHERN AND CENTRAL ROCKIES, NORTHERN PLAINS AND UPPER
MIDWEST, WITH THE GEFS SNOW WATER EQUIVALENT (SWE) PET DEPICTING SOME AREAS
WITH AT LEAST A 20 PERCENT CHANCE SWE EXCEEDS THE 85TH CLIMATOLOGICAL
PERCENTILE AND 0.5-INCHES (1-INCH ACROSS THE ROCKIES), AND THE UNCALIBRATED 0Z
ECENS DEPICTING AT LEAST A 20 PERCENT CHANCE FOR SNOWFALL GREATER THAN 4-INCHES
ACROSS THE UPPER MIDWEST DURING THE MIDDLE OF WEEK-2. THEREFORE, A SLIGHT RISK
FOR HEAVY SNOW IS POSTED ACROSS MUCH OF THE NORTHERN TIER, FEB 5-8. BOTH THE
GEFS AND ECENS PETS DEPICT AT LEAST A 20 PERCENT CHANCE 3-DAY PRECIPITATION
EXCEEDS THE 85TH CLIMATOLOGICAL PERCENTILE AND 1-INCH ACROSS PARTS OF THE
SOUTH, ALTHOUGH THESE AREAS ARE PREDICTED TO BE IN THE WARM SECTOR WITH RAIN
THE MOST LIKELY OUTCOME. THE UNCALIBRATED 0Z ECENS DEPICTS AT LEAST A 20
PERCENT CHANCE 3-DAY PRECIPITATION EXCEEDS 1-INCH EXTENDING FARTHER NORTH INTO
THE OHIO VALLEY AND NORTHEAST, WITH THE GEFS STILL MORE UNCERTAIN IN REGARDS TO
TIMING AND AMPLITUDE OF THIS POTENTIAL SYSTEM. GIVEN THE ELEVATED POTENTIAL FOR
A SYNOPTIC SCALE SURFACE LOW, A SLIGHT RISK FOR HEAVY PRECIPITATION IS
HIGHLIGHTED OVER MUCH OF THE EASTERN U.S., FEB. 5-9. THERE IS SOME RISK OF
FLOODING ACROSS PARTS OF THE MISSISSIPPI RIVER VALLEY IF THE MORE AMPLIFIED
SOLUTIONS VERIFY. EASTWARD PROGRESSION OF WINTRY WEATHER IS POSSIBLE ON THE
NORTHERN SIDE OF THE SYSTEM SUPPORTING A SLIGHT RISK OF HEAVY SNOW ACROSS NEW
ENGLAND ON FEB 7-9.
RIDGING IS FORECAST OVER ALASKA DURING WEEK-2 FAVORING RELATIVELY WARMER
TEMPERATURES OVER MUCH OF THE MAINLAND AND ALEUTIANS COMPARED TO WEEK-1.
BELOW-NORMAL TEMPERATURES REMAIN FORECAST ACROSS SOUTHEAST ALASKA, BUT HAZARDS
THRESHOLDS ARE UNLIKELY TO BE REACHED. BELOW-NORMAL PRECIPITATION IS ALSO
PREDICTED OVER MUCH OF SOUTHERN ALASKA, WITH RIDGING PUSHING HIGHER CHANCES OF
PRECIPITATION FURTHER TO THE NORTH ACROSS THE NORTHWESTERN MAINLAND.
FORECASTER: THOMAS COLLOW
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